1. Field of Invention
The invention relates to image forming devices, such as an electrophotographic copier, an electrophotographic printer (such as a laser printer and a LED printer), a facsimile machine, and a word processor.
2. Description of Related Art
As a conventional image forming device, a laser printer that forms an image on a printing medium or a recording sheet by an electrophotographic method is known.
The electrophotographic method is executed as described below. First, a photosensitive drum whose surface is uniformly charged is selectively exposed, based on image data, to a laser beam emitted from an optical mechanism (scanner). As a result, an electrostatic latent image is defined by charged portions and non-charged portions on the photosensitive drum. The electrostatic latent image is formed based on the image data. Then, when toner (developing agent) is deposited on the electrostatic latent image (charged portions) by a developing mechanism, the electrostatic latent image on the photosensitive drum is visualized as a toner image.
Thereafter, the toner image on the photosensitive drum is transferred by a transfer roller to a recording sheet. The recording sheet with the transferred toner image is heated and pressed by a heat roller and a pressure roller. As a result, the toner image is thermally fixed onto the recording sheet. By now, image forming is accomplished. The remaining toner on the photosensitive drum without being transferred to the recording sheet is removed by a cleaning blade, which is pressed against the photosensitive drum, and is stored as waste toner in a waste toner box in a process cartridge.
A process cartridge is conventionally used in this type of electrophotographic image forming device. The process cartridge into which development processing units are integrated is detachably attached to a cartridge mount in the image forming device. A development processing unit typically includes a photosensitive drum, a charger that charges the photosensitive drum, and a developing roller that supplies a developing agent to the photosensitive drum.
However, some problems may arise in the above-described image forming device when the temperature of any internal mechanism rises excessively.
For example, an optical mechanism has a polygonal mirror that reflects a laser beam and a motor that rotates the polygonal mirror at extremely high speeds. If the temperature of the motor rises excessively, the life expectancy of the motor may be shortened. Especially, when a heat roller of a fixing mechanism is heated to a high temperature by a heater, the hot air heated to the considerably high temperature accumulates at the upper portion of the fixing mechanism. If the optical mechanism is affected by such hot air, the temperature of the motor will excessively rise and the life expectancy of the motor will be shortened.
As described above, the waste toner that has not been deposited on a recording sheet is stored in the process cartridge. If the temperature of the waste toner excessively rises, the waste toner may be melted and fixed to somewhere in the process cartridge, most likely to the vicinity of the cleaning blade. If the toner is melted and fixed to the cleaning blade, the cleaning ability may be deteriorated, or the toner carrying surface of the photosensitive drum may be damaged.
The internal temperature of each mechanism is conventionally controlled using a cooling fan or the like. Recently, space has been eliminated as much as possible from image forming devices toward the downsizing of image forming devices. In addition, a compact configuration of various mechanisms in a downsized image forming device is given a higher priority than a configuration of various mechanisms for the sake of cooling efficiency. Under these circumstances, sufficient cooling effects have not yet been attained so far.
To address the foregoing problems, the present invention provides an image forming device that can efficiently cool the upper portion of a thermal fixing mechanism and an optical mechanism.
According to one aspect of the invention, an image forming device includes an optical mechanism that is disposed between a pair of support frames of the image forming device and has a drive motor that drives an optical device to form an electrostatic latent image on a photosensitive body; a developing mechanism that develops the electrostatic latent image on the photosensitive body using a developing agent; a transfer mechanism that transfers a developing agent image developed on the photosensitive body by the developing mechanism to a printing medium; a thermal fixing mechanism that thermally fixes the developing agent image transferred by the transfer mechanism onto the printing medium; an intake fan provided for one of the pair of support frames brings in cooling air from the outside of the image forming device; and an air passage that guides the cooling air taken by the intake fan to the upper portion of the thermal fixing mechanism and to the optical mechanism.
In the above-described optical mechanism, an optical device, such as a polygonal mirror that reflects a laser beam is driven by a motor to form, using a laser beam, an electrostatic latent image on the photosensitive body. The electrostatic latent image on the photosensitive body is developed using a developing agent, such as a toner, by the developing mechanism provided in, for example, a process cartridge. Then, the image formed by the developing agent on the photosensitive body is transferred to a printing medium, and the transferred image is then thermally fixed onto the printing medium.
According to the present invention, the intake fan provided for one of a pair of support frames brings in cooling air from the outside of the image forming device, the cooling air is then guided though the air passage to the upper portion of the thermal fixing mechanism and to the optical mechanism. This cooling air prevents hot air rising from the thermal fixing mechanism, therefore hot air does not accumulate in the image forming device and does not reach to the optical mechanism. In addition, the cooling air can directly cool the optical mechanism.